Recently, due to worldwide energy exhaustion, new alternative energy and a variety of methods and apparatuses for efficient energy conservation during energy circulation are actively being developed. For example, a power generation device using sunlight has been developed in priority for typical alternative energy. In the power generation device using sunlight, a solar cell for directly receiving sunlight is configured, and a storage battery is charged with electric energy from the solar cell through a constant voltage circuit which uniformly maintains a voltage generated from the solar cell, so that the electric energy can be used as an auxiliary power source when necessary.
However, power production using the solar cell has low efficiency and disadvantages in that there is a significant difference in the amount of generated power according to the amount of light and it is not possible to produce power at night. Therefore, power production using the solar cell cannot serve as a main energy source of a country and can only be an auxiliary or experimental energy source.
In addition, energy generation systems using tidal power, wind power, and water power can be used as auxiliary power sources only in regions with appropriate natural conditions. Also, resultant generated voltages do not reach expected values or are significantly limited by surroundings, and an enormous cost of initial investment in equipment is necessary. Therefore, these energy generation systems are not common.
Accordingly, recycling of energy is attracting attention as alternative energy, and due to an explosive increase in the number of vehicles used all over the world, an energy recycling system using a vehicle is required. As an example of an energy recycling system using a vehicle, such as an automobile or a train, a road power generation system for generating electric energy using vibration caused by travel of vehicles is disclosed in Korean Patent Publication No. 10-2009-01018448.
The road power generation system generates power by converting vibration energy into electric energy using resonance gradually occurring with a larger vibration width when a vehicle-passing frequency caused by repeated weights on a road resulting from travel of vehicles and the unique frequency of the road power generation system installed in the road corresponding to the vehicle-passing frequency are equalized. The road power generation system includes: a plurality of vibration plates including a central vibration portion and a protruding vibration portion at one end, and laid under the surface of a road at regular intervals in a road width direction to vibrate according to a vehicle-passing frequency caused by repeated weights on the road resulting from travel of vehicles; support fixtures installed at two or more positions in the vibration plates to support the vibration plates; a unique frequency conversion device changing the unique frequency of the vibration plates; binding support portions coupling ends of the support fixtures and the vibration plates to rotate between the vibration plates and the support fixtures; and electricity generation portions coupled to one ends of the vibration plates. The road power generation system is characterized by equalizing the vehicle-passing frequency and the unique frequency of the vibration plates corresponding to the vehicle-passing frequency and generating power with an electricity generation portion coupled to a resonating vibration plate.
However, the road power generation system has a structure which generates power using vibration caused by travel of vehicles, and impact power caused by travel of vehicles is directly transferred to vibration plates. Therefore, the road power generation system has problems of deformation and damage caused by impact power.
As another example, Korean Patent Publication No. 10-2009-0121850 discloses an electric automobile having a hydraulic power generation system. The electric automobile having a hydraulic power generation system includes: a driving motor coupled to a driving wheel to transfer turning force; a decelerator installed between the driving motor and the driving wheel to change the turning force; a storage battery supplying power to operate the driving motor; a second driving motor connected to the storage battery to operate; a hydraulic pump receiving turning force from the second driving motor to compress oil and having an inflow port and an outflow port formed therein; an oil tank supplying the oil to the inflow port of the hydraulic pump; a hydraulic motor rotating due to a hydraulic pressure applied from the hydraulic pump; a power transfer portion including a drive gear and one or more driven gears installed at the hydraulic motor and an axis to transfer turning force; and one or more power generators connected to the power transfer portion to rotate and charge the storage battery with generated power.
However, the hydraulic power generation system has a structure in which the hydraulic pump is operated using electricity stored in the storage battery, the hydraulic motor is driven by the hydraulic pump, and power is generated by the power generators coupled to the hydraulic motor to charge the storage battery, that is, a structure in which power is generated using electricity stored in the storage battery and stored in the storage battery again. Therefore, power generation efficiency is low, and fuel-efficiency of a vehicle is degraded because heavy equipment, such as the second driving motor, the hydraulic motor, and the oil tank, should be mounted in the vehicle.